Polyurethanes were synthesized from polyester polyols, derived from PET waste. The PET waste was first depolymerized by glycolysis. The glycolysized products were reacted with adipic acid to yield polyester polyols, and the polyester polyols were then reacted with either MDI or TDI to obtain polyurethanes. In this article, the thermal properties of the polyurethanes obtained are discussed in detail.